全文获取类型
收费全文 | 8090篇 |
免费 | 735篇 |
国内免费 | 400篇 |
专业分类
电工技术 | 511篇 |
综合类 | 593篇 |
化学工业 | 1436篇 |
金属工艺 | 345篇 |
机械仪表 | 413篇 |
建筑科学 | 588篇 |
矿业工程 | 213篇 |
能源动力 | 284篇 |
轻工业 | 672篇 |
水利工程 | 129篇 |
石油天然气 | 270篇 |
武器工业 | 39篇 |
无线电 | 888篇 |
一般工业技术 | 981篇 |
冶金工业 | 435篇 |
原子能技术 | 153篇 |
自动化技术 | 1275篇 |
出版年
2024年 | 9篇 |
2023年 | 78篇 |
2022年 | 243篇 |
2021年 | 317篇 |
2020年 | 216篇 |
2019年 | 223篇 |
2018年 | 225篇 |
2017年 | 235篇 |
2016年 | 218篇 |
2015年 | 307篇 |
2014年 | 349篇 |
2013年 | 468篇 |
2012年 | 495篇 |
2011年 | 523篇 |
2010年 | 488篇 |
2009年 | 407篇 |
2008年 | 429篇 |
2007年 | 432篇 |
2006年 | 359篇 |
2005年 | 257篇 |
2004年 | 304篇 |
2003年 | 425篇 |
2002年 | 554篇 |
2001年 | 498篇 |
2000年 | 221篇 |
1999年 | 160篇 |
1998年 | 145篇 |
1997年 | 101篇 |
1996年 | 85篇 |
1995年 | 73篇 |
1994年 | 49篇 |
1993年 | 64篇 |
1992年 | 38篇 |
1991年 | 16篇 |
1990年 | 35篇 |
1989年 | 30篇 |
1988年 | 6篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 14篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1975年 | 7篇 |
排序方式: 共有9225条查询结果,搜索用时 31 毫秒
31.
32.
Pierre Darcy Patrick Da Costa Henry Mellotte Jean-Michel Trichard Grald Djga-Mariadassou 《Catalysis Today》2007,119(1-4):252-256
To comply with the new regulations on particulate matter, car manufacturers more and more commonly use diesel particulate filters (DPF). The working of these systems needs to periodically burn soot that has been accumulated during the loading of the DPF. This paper describes the kinetics of the non-catalytic and catalytic oxidation of real diesel soot with oxygen. From these experiments, mechanisms for catalyzed and non-catalyzed soot oxidation have been proposed. 相似文献
33.
本文着重对图象多分辨率技术进行分析,并提出了相应的系统结构成框架,同时还探讨了以图象多分辨率处理为核心,采用了 新的压缩编码的可能性。 相似文献
34.
Coupling GIS with Hydrologic and Hydraulic Flood Modelling 总被引:6,自引:1,他引:5
Nunes Correia Francisco Castro Rego Filipe Da Grača Saraiva Maria Ramos Isabel 《Water Resources Management》1998,12(3):229-249
Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management. 相似文献
35.
Accelerated reliability tests on thin oxide capacitors can be affected by series resistance effects at high stress conditions. The purpose of this work is to point out such problems both with measurements and simulations. It is shown that breakdown electric field is overestimated. Due to the resulting nonuniform stress, charge to breakdown density is underestimated if the test structure layout is not accurately designed. In any case the series resistance effects can have an undesirable impact on the reliability evaluation of thin dielectrics. 相似文献
36.
A Colli M Cocciolo C Riva L Marcassoli M Pirola P Di Gregorio G Buccino 《Canadian Metallurgical Quarterly》1993,72(3):677-682
BACKGROUND: Ascites in patients with hepatocellular carcinoma (HCC) is a poorly characterized subgroup of malignancy-related ascites. Not only the underlying liver disease, but also the tumor growth and spread contributes to the ascites formation. The authors differentiated ascites in HCC from other types of ascites. METHODS: The authors analyzed the ascitic fluid of 185 consecutive patients (89 liver cirrhosis, 33 HCC, 31 peritoneal carcinomatosis, 22 liver metastases, 10 spontaneous bacterial peritonitis). RESULTS: Each subgroup showed a typical pattern. Compared with the cirrhotic patients, those with HCC showed a higher frequency of positive cytologic findings (4 of 33 versus 0/89, P < 0.004), elevated fibronectin concentration (10/33 versus 8/89, P < 0.004), and elevated polymorphonuclear cell count (10/33 versus 5/89 P < 0.004). CONCLUSIONS: A significant number of patients with ascites and HCC patients showed signs of peritoneal infiltration with positive cytologic findings and increased concentration of fibronectin. Moreover, neutrocytic ascites without signs of superinfection is relatively common (30%). 相似文献
37.
相转移法制备高纯超细TiO2技术研究 总被引:9,自引:0,他引:9
报道了用相转移法制备高纯超细TiO2的新技术;探讨了Ti(Ⅳ)从有机相转移到水相发生水解反应的机理 ;通过TG-DTA分析以及XRD物相分析对水解产物的组成、热分解机理,晶型转变规律进行了研究,建立了水解产物焙烧的最佳温度。 相似文献
38.
39.
湿化学法制备纳米ATO导电粉 总被引:19,自引:0,他引:19
采用非均相成核法 ,在Sn(OH) 4 晶种上均匀生长Sb掺杂Sn(OH) 4 ,制备纳米ATO粉末。以电阻测定系统研究了合成条件如掺杂浓度、反应温度、pH值、SnCl4浓度等对最终粉末电阻性能的影响。以TG DSC热分析、XRD、TEM等手段研究了晶粒生长过程 ,XRD显示为四方金红石型结构 ,平均粒径为15nm。当Sb/Sn(mol比 ) =0 .0 5 ,pH =2 ,T =60℃ ,SnCl4=1.2~ 1.8mol·L-1时 ,粉体电阻小于 0 .5Ω。 相似文献
40.
Da SHU Baode SUN Ke LI Jun WANG Yaohe ZHOUState Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University Shanghai China 《材料科学技术学报》2003,19(3):221-225
The continuous separation of inclusions from aluminum melt flowing in a circular pipe using a high frequency magneticfield was investigated both theoretically and experimentally The separation efficiency was calculated based on thetrajectory method and compared with experimental results. It is found that the separation efficiency is a functilnondimensional parameters t_i·d_p~2B_e~2/μ_fμ_eα~2 and α/δ.The effective way to improve the separation efficiency is to increasethe effective magnetic flux density and decrease the pipe radius. and the value of α/δ should be kept about 2 in orderto obtain the optimum separation efficiency. 相似文献